scsi: ufs: core: Initialize devfreq synchronously

scsi: ufs: core: Initialize devfreq synchronously

During UFS initialization, devfreq initialization is asynchronous:
ufshcd_async_scan() calls ufshcd_add_lus(), which in turn initializes
devfreq for UFS. The simple ondemand governor is then loaded. If it is
built as a module, request_module() is called and throws a warning:

  WARNING: CPU: 7 PID: 167 at kernel/kmod.c:136 __request_module+0x1e0/0x460
  Modules linked in: crct10dif_ce llcc_qcom phy_qcom_qmp_usb ufs_qcom phy_qcom_snps_femto_v2 ufshcd_pltfrm phy_qcom_qmp_combo ufshcd_core phy_qcom_qmp_ufs qcom_wdt socinfo fuse ipv6
  CPU: 7 PID: 167 Comm: kworker/u16:3 Not tainted 6.2.0-rc6-00009-g58706f7fb045 #1
  Hardware name: Qualcomm SA8540P Ride (DT)
  Workqueue: events_unbound async_run_entry_fn
  pstate: 00400005 (nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
  pc : __request_module+0x1e0/0x460
  lr : __request_module+0x1d8/0x460
  sp : ffff800009323b90
  x29: ffff800009323b90 x28: 0000000000000000 x27: 0000000000000000
  x26: ffff800009323d50 x25: ffff7b9045f57810 x24: ffff7b9045f57830
  x23: ffffdc5a83e426e8 x22: ffffdc5ae80a9818 x21: 0000000000000001
  x20: ffffdc5ae7502f98 x19: ffff7b9045f57800 x18: ffffffffffffffff
  x17: 312f716572667665 x16: 642f7366752e3030 x15: 0000000000000000
  x14: 000000000000021c x13: 0000000000005400 x12: ffff7b9042ed7614
  x11: ffff7b9042ed7600 x10: 00000000636c0890 x9 : 0000000000000038
  x8 : ffff7b9045f2c880 x7 : ffff7b9045f57c68 x6 : 0000000000000080
  x5 : 0000000000000000 x4 : 8000000000000000 x3 : 0000000000000000
  x2 : 0000000000000000 x1 : ffffdc5ae5d382f0 x0 : 0000000000000001
  Call trace:
   __request_module+0x1e0/0x460
   try_then_request_governor+0x7c/0x100
   devfreq_add_device+0x4b0/0x5fc
   ufshcd_async_scan+0x1d4/0x310 [ufshcd_core]
   async_run_entry_fn+0x34/0xe0
   process_one_work+0x1d0/0x320
   worker_thread+0x14c/0x444
   kthread+0x10c/0x110
   ret_from_fork+0x10/0x20

This occurs because synchronous module loading from async is not
allowed. According to __request_module():

  /*
   * We don't allow synchronous module loading from async.  Module
   * init may invoke async_synchronize_full() which will end up
   * waiting for this task which already is waiting for the module
   * loading to complete, leading to a deadlock.
   */

Such a deadlock was experienced on the Qualcomm QDrive3/sa8540p-ride. With
DEVFREQ_GOV_SIMPLE_ONDEMAND=m, the boot hangs after the warning.

Fix both the warning and the deadlock by moving devfreq initialization out
of the async routine.

Tested on the sa8540p-ride by using fio to put the UFS under load, and
printing the trace generated by
/sys/kernel/tracing/events/ufs/ufshcd_clk_scaling events. The trace looks
similar with and without the change.

Link: https://lore.kernel.org/r/20230217194423.42553-1-athierry@redhat.com
Signed-off-by: Adrien Thierry <athierry@redhat.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>